Quarries and subsoil of Paris’s 5th arrondissement
High risk Paris 75005
The 5th arrondissement, on Sainte-Geneviève hill, is one of Paris’s oldest areas of Lutetian coarse limestone extraction. From Gallo-Roman times onwards, building stone was quarried there, then from the 12th century the quarries became underground. The 5th is part of the Grand Réseau Sud (GRS), which covers approximately 508 hectares and 200 km of galleries. The areas around Val-de-Grâce, rue Mouffetard and place Monge are particularly affected. A construction or renovation project in the 5th requires an investigation of the subsurface before any planning permission is granted.
What public data say about the 5th
| Underground network | Grand Réseau Sud (GRS) |
|---|---|
| Mined rock | Lutetian coarse limestone |
| Undermined area | Part of the ~508 ha Grand Réseau Sud (5th, 6th, 14th, 15th). |
| Galleries | Included in the GRS’s ~200 km of galleries. |
| Selected risk level | High |
| Confidence in the classification | high |
| Nature of the ground | Lutetian limestone plateau (Sainte-Geneviève hill) |
| Foundation issue | Limestone ground is generally load-bearing outside cavity areas. The established presence of galleries requires a prior check with the IGC (Paris quarry inspectorate) before any project; a G2 geotechnical study remains recommended. |
Sensitive areas of the 5th
- Sainte-Geneviève hill (Val-de-Grâce, rue Mouffetard, place Monge)
- Quarries mined from Antiquity onwards, becoming underground in the 12th century
Documented events in the 5th
1st–3rd c.
Ancient limestone quarrying
Sainte-Geneviève hill (5th)
From the Gallo-Roman period onwards, the limestone of the Sainte-Geneviève hill (5th) and the gypsum of the Montmartre hill (18th) were mined for building stone and plaster.
Source: City of Paris — Everything you need to know about the subsurfaces
December 1774
Subsidence of route d’Orléans
Barrière d’Enfer (5th/14th)
Widespread subsidence of the route d’Orléans over more than 300 metres in length. This event triggered the creation of the IGC (Paris quarry inspectorate) in 1777.
Source: Institut Paris Région — Underground risk study (quarries) · Annales des Mines — The Quarry Service
1774 (detail)
Collapse on rue d’Enfer (300 m)
rue d’Enfer / av. Denfert-Rochereau (5th/14th)
On 17 December 1774, a quarry excavation caused the collapse of rue d’Enfer (now avenue Denfert-Rochereau). Nearly 300 metres of road disappeared into a considerable excavation. The direct catalyst for the creation of the IGC (Paris quarry inspectorate).
Source: Le Figaro — The burdensome legacy of Paris’s Swiss-cheese subsurfaces · Catacombs of Paris (official website) — History of the site
Ground, fill and clay shrink-swell
The 5th arrondissement sits on the Lutetian coarse limestone plateau of Sainte-Geneviève hill, rock that is generally load-bearing at depth but excavated by the Grand Réseau Sud (see the quarries section). Plastic clay was historically extracted on the edge of the Bièvre valley, to the south.
Limestone ground is generally load-bearing outside cavity areas. The established presence of galleries requires a prior check with the IGC (Paris quarry inspectorate) before any project; a G2 geotechnical study remains recommended.
Unlike almost all French municipalities, inner Paris has no official mapping of the clay shrink-swell hazard (RGA). The BRGM explains this explicitly: the Paris subsoil is largely made up of reworked and artificial materials (backfill, infilled former quarries), which does not correspond to the standard methodology for this mapping — centred on detached houses, which are in the minority in Paris. This does not mean that there is no risk of differential settlement, but that no official area-by-area study exists for the capital: a ground investigation remains the only reliable way to assess a specific plot before purchase or construction.
Your procedures in the 5th before a purchase or works
Before any purchase or construction project: (1) consult the IGC (Paris quarry inspectorate) (igc.paris.fr) to request information on the parcel’s subsoil; (2) have a G1 geotechnical study carried out by a certified engineering consultancy; (3) check the statutory risk statement (ERP) via Errial.
- IGC (Paris quarry inspectorate) information sheet — the authoritative source on the condition of the parcel’s subsoil: €10, issued within 8 days, via the City of Paris online service.
- Statutory risk statement (ERP) — mandatory for sale and letting, generated from Errial; note, it does not return cavity data in Paris.
- geotechnical survey — G1 mission before purchasing a building plot, G2 AVP before a construction or underpinning project.
- Referral to the IGC (Paris quarry inspectorate) for planning — prefectoral orders require it to be consulted for any planning permission in a quarry-risk area.
Frequently asked questions
Are there underground quarries beneath Paris’s 5th arrondissement?
Yes. The 5th arrondissement is listed in the public data of the IGC (Paris quarry inspectorate) as an area affected by the network « Grand Réseau Sud (GRS) », in Lutetian coarse limestone. The assigned risk level is « High », with high confidence in the sector’s classification. Sainte-Geneviève hill was quarried as early as the Gallo-Roman period for building stone. Historic heart of the southern network.
How can I tell whether my exact address in the 5th is in an undermined area?
Quarry zoning must be read at plot level rather than arrondissement level. There are two options: the official information sheet from the IGC (Paris quarry inspectorate), at €10 and issued within 8 days, which is the legally binding source; and Sous-sol Paris’s instant pre-assessment, at €15, which matches your address against public data and immediately provides you with a readable report, including the steps to take. This pre-assessment is for information only and does not replace the IGC information sheet, the statutory risk statement (ERP), or a geotechnical study.
Why do cavity data for the 5th not appear on Géorisques?
Because for départements 75, 78, 91, 92, 93, 94 and 95, cavity data are not published on the Géorisques portal: they can be consulted with the IGC (Paris quarry inspectorate) for Paris and the inner suburbs, or with the relevant interdepartmental service. This is why a standard statutory risk statement (ERP) remains silent on Paris quarries and gypsum.
Is quarry risk in the 5th covered by insurance?
Disorders linked to former quarries do not fall under the « natural disaster » scheme. In the event of collapse, infill works, estimated at 40 000 to 200 000 €, remain the responsibility of the owners. This is what makes checking before purchase essential.
Other arrondissements
- Subsoil of the 4th arrondissement
- Subsoil of the 6th arrondissement
- Subsoil of the 3rd arrondissement
- Subsoil of the 7th arrondissement
- Subsoil of the 12th arrondissement
- Subsurface of the 13th arrondissement
- Subsoil of the 14th arrondissement
- See the 20 arrondissements
Sources
- City of Paris — Everything you need to know about the subsurfaces
- Institut Paris Région — Underground risk study (quarries)
- Wikipedia — Underground quarries of Paris
- Wikipedia — Paris, Geology section
- BRGM InfoTerre — Explanatory note for the 1/50000 geological map of Paris
- BRGM — Why is there no map of the clay shrink-swell hazard for Paris?
- Géorisques — Clay shrink-swell, 2026 version (data)
- Annales des Mines — The Quarry Service
- Le Figaro — The burdensome legacy of Paris’s Swiss-cheese subsurfaces
- Catacombs of Paris (official website) — History of the site
- Géorisques — Underground cavities (data)
- City of Paris — the IGC (Paris quarry inspectorate) location
- City of Paris — Known areas of former quarries (IGC)
Page updated on 11 September 2026.